1. Field of the Invention
The present invention relates generally to printer registration marks, and more specifically to a method for applying printer registration marks to linerless label stock.
2. Description of Related Art
Linerless media and labels are becoming increasingly popular in the label producing industry because of the many advantages over their linered counterparts. A linerless label stock is typically a continuous roll of direct thermal label or tag stock (e.g., paper, film, or combination) having a pressure sensitive (i.e., self-stick) adhesive on the backside without a silicone coated release liner. Linerless label stock is advantageous over traditional linered media since there is no release liner to dispose of, and as a result, a greater amount of media may be included in a same size roll as that of linered media. In view of the growing popularity of linerless media, methods to improve the production and throughput rates of linerless labels have become essential.
The linerless label stock is transported through a printing system including a printer such as a thermal transfer or direct thermal printer. In a thermal transfer printer, the linerless label stock is transferred through the print region of the printer along with a thermal transfer ribbon. The thermal transfer ribbon is impregnated with a thermally sensitive chemical that reacts in the presence of heat applied by print elements of the print region. The chemical is then transferred onto the linerless label stock in the form of printed indicia. In a direct thermal printer, the thermally sensitive chemical is impregnated directly into the linerless label stock, thereby eliminating the need for a separate thermal transfer ribbon. Both types of printing are collectively referred to herein as thermal printing. Under either method of thermal printing, the thermal printer creates the printed indicia by selectively controlling individual ones of the print elements. The printed indicia may take the form of individual labels provided on designated sections of the linerless label stock with a gap defined between adjacent ones of the labels.
Unlike linered labels that are pre-cut to size, the individual labels of linerless label stock must be separated after printing. Some printers for linerless media use an automatic rotary or guillotine type cutter knife mechanism to separate the labels from the continuous label stock. These cutter mechanisms can be costly and difficult to keep clean of adhesive residue. Other printers use a manual tear bar, which is a stationary blade that is used to cut the label stock by manually pulling the media across the tear bar. These tear bars do not always give a consistently clean tear across the label stock. Also, the tear bar may have a serrated knife that can pose a risk of serious injury to users of the printer. Thus, a preferred method to produce individual labels is to pre-cut a perforation line into the label stock. The perforation line allows for easy, clean separation of individual labels or tags. The perforation lines must be recognized by the printer so that the printed indicia can be aligned to the predetermined labels defined by the perforation lines without extending over the perforations lines. Thus, it is known to include printer registration marks onto a roll of linerless label stock disposed in correspondence with the perforation lines. The registration marks may be detected by optical sensors included within the printer used to print indicia upon the linerless label stock.
A known way to apply registration marks to linerless media is to print the marks onto the back of the label stock before the adhesive is applied to the label stock. Linerless media manufacturers typically apply the adhesive coating to large sheets of the media that are later cut down to the desired width dimensions of the linerless label stock and wound onto rolls or spindles. The adhesive coating equipment is generally large and expensive, and it is thus impractical for small scale label manufactures or printer end-users to perform. Another drawback of having registration marks pre-printed on the linerless media prior to applying the adhesive layer is that it limits the eventual printing of labels to the particular dimensions determined by the registration marks. An alternative method is to place registration marks on the facing surface of the label stock. This is undesirable because the registration marks have the potential to interfere with the printed indicia, such as barcodes, that are printed onto the labels. Thus, there is a need for a method to apply printer registration marks onto the backs of the linerless labels after the adhesive has been applied.
Therefore it is an object of this invention to provide a process for applying printer registration marks to linerless label stock so that the resulting labels can be produced in a fast, efficient manner. It is further an object of this invention to provide an economical process for applying printer registration marks onto linerless label stock.